(Benchmark) Hardest case for solver (Fix #15)
(Benchmark) Hardest case for solver (Fix #15)

- The two FEs in this example are "interlaced".
- Combined with the particular values for the LHS, solving this will
take a lot of iterations...

In this extreme case, any direct method (areg, projvar, felsdvreg?) is
better than an indirect method.

- Note that CG+SYM is still fast, SD+KAC slow, and AITKEN+anything is
very slow
- Also note that a simple GT preconditioner for CG+SYM fixes this
problem

tonijung/reghdfe,tonijung/reghdfe,sergiocorreia/reghdfe